reserve a,b,c for set;

theorem Th40:
  for D being non empty set,f,CR being File of D holds
  CR is_substring_of addcr(f,CR),1
proof
  let D be non empty set,f,CR be File of D;
  addcr(f,CR)=ovlcon(f,CR) by FINSEQ_8:def 11;
  hence thesis by Th39;
end;
